It is generally well known that combustible material introduced through a tuyere into a reducing furnace requires proper atomization and mixing. By utilization of a supersonic nozzle wherein a shock wave is produced in the divergent portion, atomization and mixing are optimized. Typically, however, the construction of such nozzles has been with relatively limited parameters precluding any useful variation in the flow rates of the combustible material.
Recently, a method and apparatus have been proposed for the operation and construction of a tuyere in which relatively wide variations in the flow rate of combustible material is permitted while at the same time forming the necessary shock wave in the divergent portion of the nozzle for proper atomization. See U.S. Pat. No. 3,771,473, where the convergent portion of the supersonic nozzle is modifiable by axially adjusting a central body portion arranged substantially coaxially in the convergent portion.
The device shown in U.S. Pat. No. 3,771,473 is useful in applications such as a blast furnace; it has limited application, however, in tuyeres for refining vessels, in particular, submerged blowing steelmaking vessels. In a submerged blowing steelmaking vessel, a common problem is that the velocity of the exiting gas, such as oxygen, from the tuyere is not sufficient to prevent the erosion of the refractory material. It is, therefore, desirable to produce a tuyere structure in which the gas blown into the hot metal exits therefrom at a supersonic velocity. However, since the tuyeres in a submerged-blown vessel are consumed together with the refractory material, prior art tuyere nozzles which provide a supersonic flow are consumed well before the end of the useful life of the tuyere. Furthermore, in some applications it is desirable to introduce into the tuyere a combustible material which must be properly atomized for supersonic injection into the hot metal. Moreover, while it is necessary to provide supersonic velocities of the fluid blown into the metallurgical vessel, it is frequently required that velocities less than supersonic be provided or be possible.
Accordingly, it is an object of the present invention to provide a nozzle means capable of producing a supersonic jet of gas at the end of an erodible tuyere. It is another object of the invention to provide a nozzle means which is capable of providing an optimized supersonic velocity that is selectively reducible by adjusting the position of the nozzle means. It is a further object of the present invention to provide a nozzle means wherein a combustible material may be properly atomized at varying flow rates while maintaining supersonic injection at the output end of a constantly erodible tuyere.